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Monday, 22 August 2016

Building a MPCNC part 2

After using my MPCNC bolted to the workbench last time, we had a bit of a heat wave here and the electrical tape I'd used in constructing the cables failed, turns out the adhesive is temperature sensitive. After unbolting it from the bench to check the connections on the x2 motor, I decided to make the machine more mobile, and a bit of research turned up slotted 3/4" MDF at the local hardware store, perfect for making the waste board top from.

Gluing and screwing the base board together

The final version of the base ended up being made of the 3/4" MDF glued to a 3/4" thick sheet of plywood, total thickness 1.5 inches, glued and screwed together. The result is a perfectly flat sheet that weighs about 20 pounds and takes two people to move, but it doesn't shake or move during operation. For solving the electrical problem, I found some 22-gauge wire crimp connectors when I picked up the MDF.

After letting the glue on the baseboard dry overnight, I screwed the feet of the MPCNC's frame into place and squared things up again, adding some extra screws through the ends of the outer rods to lock things down permanently.

Corner with rod locking screws installed

Once the frame was fully installed, I started printing some drag chains and mounts that I found on Thingiverse (Drag Chain, Z-Mount, XY-Mounts), took about 400 grams of filament all told. The XY mounts are designed around the older version of the MPCNC's roller carriages from before the 7/16 update, so the hole spacing was off by 1/4" but a few minutes work with a file fixed that issue. I also had to replace the 1.25" bolts on the back of the roller carriages with 2" ones, although it turns out that 1.5" ones would have worked just fine. I just used a couple of spare 6-32 screws and bolts left over from the initial assembly to secure the chain to the mount.

Drag chains waiting for installation

Drag chain mount fully installed

X axis drag chain fully installed

After installing the drag chains, it was time to install the electronics housing. I'd printed a Ramps case from Thingiverse, and after a bit of modifying with a hand saw, I screwed it to a spare piece of plywood that is fixed on one corner of the base. Wiring up a Ramps 1.4 set is fairly straightforward (see Reprap.org). Only thing left was to assemble the hold-down clamps.

Hold-down clamp parts

I decided to use a combination of a printable Shapeoko Clamp (red in the picture) and this knob (silver in the picture). Add a 5/16" washer, 1/4" nut, and 2"x1/4" carriage bolt, and it makes a simple, solid hold-down for anything up to 1 inch thick.

Hold-down assembled

Full set of hold-downs

After all that, only thing left was to start things up and make something! I found a RIGID palm router on craigslist and installed it for use as a spindle, cuts through wood without any difficulty.